Process and apparatus for regulating chemical reactions



Dec. 10,1929, K. c. D. HICKMAN PROCESS AND APPARATUS FOR REGULATINGCHEMICAL REACTIONS Filed Aug. 1, 1927 gwue'ntoa Kenneth G D. Hichmam WPatented Dec. 10, 1929 UNITED STATES "PATENT OFFICE KENNETH C. D.HICKMAN, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK I COMPANY, OFROCHESTER, NEW YORK, A CORPORATION OF NEW YORK i PBOCESS AND APPARATUSFOR REGULATING CHEMICAL REACTIONS Application filed August 1,

This. invention relates to processes and apparatus for regulatingchemical reactions. It finds its present field'of greatest usefulness.in regulating the titration of streams of redicate thestage of thereaction by altering the conductivity of a separate electrolytic cell.Still another object of the invention is to provide a process andapparatus in which streams of reagents are titrated against eachotherand any excess flow of a'stream is auto matieally corrected,the-presence or absence of gas from the reaction mixture altering theconductivity of a separate electrolytic cell, and the latter controllingthe flow of one of the streams relative to the others,-in other words,the cell acts as an electrolytic nose to examine the condition of thereaction mixture by"smelling the gas evolved. Still another object is toprovide such an apparatus and process in which the electrolyte in thecell is continuously changed so that successive amounts of gas from thereaction mixture will pass into separate portions of electrolyte. Otherobjects will hereinafter appear.

In the accompanying drawing,

Fig. 1 is.a diagrammatic sectional View inlustrating one form ofapparatus in which my invention may be embodied and carried out;

Fig. 2 is a side elevation of a stream regulator which is readilycontrolled.

In conductingchemic'al reactions, especially those in which one liquidis titrated against others, the presence or absence of an excess of saidliquid has been customarily indicated by a color indicator. In someinstances electrical conductivity measurements have been made, but sofar as I am aware, these have been made directly upon the reactionmixture of the liquids. For many .types of reactions, and especiallywhere exact control is essen- -1y intor the entire.body o 1927. SerialNo. 209,807.

tial, such measurements on the reaction mixture are troublesome andsubject to error.

i In contradistinctionv to such measurements on the reaction mixture,which may be called internal indications, I employ an externalindicator, and measure the conductivity of an *electrolyte in a cellseparate from the reaction mixture and into which any gas from thereaction mixture passes. It is, therefore,

; essential in my process thatv one of the reagents, or else the productof the reaction, shall contain a volatile or gaseous material .which,when dissolved inthe electrolyte of the cell, will display-acharacteristic conductivity. Itis convenient to conduct any such gas orvapor from the reaction mixture to the electrolyte in the indicator cellby means of a current of air or inert gas. 4

There are many reactions to which my process and apparatus may beapplied. Typical of the reactions in which one of the reagents containsa volatile gas is the following:

. n2so..+2uH,oH= iu-i;; .so..+ 211.0

An aqueous solution of sulfuric acid is mixed with ammonia water. If theammonia water is run into the sulfuric acid there will be no gas presentin the reaction mixture, as long as the sulfuric acid is in excess. Butwhen the reaction reaches the stage where the sulfuric acid is whollyneutralized, further addition of ammonia water will provide an amount offree ammonia gas :at the reaction mixture. If this gas be conducted,such as by a stream of air, intoan electrolytic cell containing anaqueous electrolyte, including even plain water, it will greatlyincrease the conductivity of. said electrolyte, and thus show that thereaction has reached the neutralization stage. It is preferable to passa into the detectioncell, so that the latter will,

by its increased conductivity, Show instantly when the first amount ofammonia is given off. 4

Instead of pouring one ingredient gradualthe other, two streams of themmay be mixed, in fact, I find this to be the most practical method. 1

The streams are first thoroughly mixed, and

any gases that may be present-at the reaction mixture are swept by astream of air into an electrolytic cell in which the electrolyte is Butsmall amounts of ammonia may beadded to either solution, and being aweak base will be evolved from the reaction mixture as soon as thealkali is in even slight excess.

Instead of an alkaline indicating gas, like ammonia, I may employ anindicating gas of .an acid nature, such as sulfur dioxide, which isfound to be remarkably effective in its rapid indication in the cell.For example, in the reactionbetween sulfuric acid and sodium hydroxide,the formulae .of which are given above, a small amount of sodium sulfitemay be added. The instant that the reaction mixture becomes acid, S0 isevblved, and being swept into the water of the detection cell, thelatter instantly indicates that the acid stage of the reaction has beenreached. 4

Not only has the method been found useful in ordinary reactions betweenacids and alkalies, but it is very useful in reactions between oxidizingand reducing substances, such as when titrating calcium oxychlorideagainst a sodium thiosulfate solution, or a solution of potassiumpermanganate against a solution of sulfurous acid or acid sodiumsulfite. Chlorine andbromine alter the conductivity of the water in thedetection cell with satisfactory rapidity, as well as'gases hereinabovementioned.

WVhile my method and apparatus are useful When the conductivity of thedetection cell is merely used as an indication, I greatly prefer to usesuch cell in automatically regulating the proportions of the reagents inthe reaction mixture. latricnlarly when titrating streams of liquid itis desirable to have the cell connected with apparatus which detailsthus given, except as indicated in the appended claims. The first reaent 1 flows from the storage tank 2' through pipe 3 into preliminarymixing chamber 4 where it mingles with the other reagent 5. The lattercomes from storage tank 6 through the flow regulator 7 and pipe 8. Asshown in the drawing, it is referable to have the stream of reagent 5 owupwardly against the descending stream of reagent '1. Obviously anymeans of thoroughly mixing the reagents can be employed.-

From the preliminary mixing chamber 4 the reaction mixture passes intofinal reaction chamber 9 where it passes downwardly in the form of sprayand is finally drawn off through pipe 10 to any-convenient storagevesesl (not shown). In'the top of the final mixing chamber 9 is avertical descending pipe 11, the bottom of which is conveniently flared,as shown 'at 12. If air entering with the reagents-from the preliminarymixing box 4 'into chamber 9 is insuflicient, a sma air vent 111 may beprovided in the side of chamber 9, but this is usually not necessary.The pipe 11 opens into a liquid separator chamber 13, the latterbeingconnected with the lower part of chamber 9 by means of pipe 14. Theseparator 13 is connected by pipe 15 with the electrolytic detector cell16. The latter receives its water or aqueous electrolyte through pipe17, the entrance to which from the water supply is controlled by aneedle valve 18 operated by handle 19 Below the valve 18 the pipe 17 isconnected by pipe 20 with a suction device 21 which, as shown, mayconveniently take the form of an aspirator or so-called Water vacuumpump. The water from the aspirator passes into chamber 22 on its way tothe discharge 23, and the supply of water for the electrolytic cell maybe obtained from 22, as shown. The detector cell 16 comprises twoelectrodes 24 connected by leads 25 with a circuit containing a solenoid26 and a lamp 27 There may convenient'iy be arranged a switch 28whiclris normally closed and leads 25 may be connected with a suitablesource of either direct or alternating current. lVithin thesolenoid 26.is a plunger 29 connected by a wire. or link 30 with the arm 31 of theflow control 7. s

The flow control comprises a cylindrical vessel 32 rotated aboutitshorizontal axis in any suitable bearings within a tank or container 33.Vessel 32 is provided with radially extending discharge openings 34.

The tank 33 is provided with a vertical partition 35 and one of thedischarge openings empties the liquid into that part of the tank 33which is connected to thepreliminary mixing chamber 4 through pipe 8.The

other discharge opening 34 empties the liquid v into thatpart of thetank 33 which is connected with the pipe 36, which may lead process iscarried out.

to any suitable storage receptacle, not shown, or any return pipingsystem for bringing theliquid back to storage tank 6. A spring 37normally tilts the cylinder 32 in such a position that it roduces themaximum discharge into the plpe 8, with little or no liquid sequentlythe out-flowing streams from cylinder 32 do not tend to rotate thelatter, in other words, do not interfere with the automatic regulation.7

The water'from the cell 16 passes by pipe 38 into the trapped pipe 39.From the juncture of pipes 38 and 39 there is a connection passingaround the top of the cell-to equalize the pressure.

Referring to Fig. 2 for further details of the stream regulator, it willbe noted that the tank 33 is provided with observation windows 41through which may be observed the radial openings 34. The axle 42 of thecylinder 32 rests in any suitable bearing 43 of minimum friction. Upwardfrom the axle 42 is an extension 44 on the top of which is fastened thelever 31. The cylinder 32 is open at the top so that the descendingliquid 5 from storage tank 6 may drop freely into it without anymechanical connection between said tank 6 and cylinder 32.

I shall now describe briefly the operation of this apparatus, in whichmy novel A solution of sulfuric acid is, for instance, charged into tank2 and a batch ofammonia water is charged into tank 6. The acid andammonia solutions meet and react'with each other in the preliminary mix.ing box 4. Owing to spring 37, the cylinder 32 is in'theposition to feedenough neutralizing ammonia solutionthrough pipe 8 to the mixing box.The reaction mixture then flows into the final. reaction chamber 9around th flared end of- 12 of pipell.

The aspirator 21 being in operation and the valve 18.being'properlyregulated, there is a partial vacuum created in pipes 17, l5, l3 and 11and yet drops of water pass downwardly by gravity through the pipe 17into the cell 16. While the water might be conducted downwardly by aseparate'pipe from that through which the vacuum is transmitted, it

has been found in actual practice that the creation of the vacuum doesnot interfere with' 4 and flowing over the end of pipe 11 is inexcess,ammonia gas will be present in the final reaction chamber 9 and will bedrawn I have found that this cylinder by the vacuum through pipes 11 and15 through the top of cell 16 into pipe 17, where it dissolves in thewater descending tothe cell. This electrolyte then flows through thecell 16 and outward through the-pipes 38 and 39.

As the electrolyte containing the ammonia.

passes between the plates-24, the resistance of the cell is greatlylessened and an increased current passes through the solenoid 26 andlamp 27. This pulls downwardly upon the soft steel plunger 29 and thewire 30, and consequently pulls downwardly on lever 31 and tilts thecylinder32 against the action of spring 37 so as to lessen the flow ofammonia water in the pipe 8. 5

As soon as the excess of ammonia water is thus removed, and a normalbalance in the titration reaction is obtained, no ammonia gas is drawnwith the air through pipes 11 and 15 and consequently the water passingthrough thecell 16 has a much higher resistance. This causes the currentthrough the solenoid 26 to be diminished and the spring 37 consequentlyrocks the cylinder 32 so as to increase the amount of ammonia waterwhich passes into pipe 8 and thence to the reaction chambers. It will benoted that the lamp 27 not only serves as a resistance to lower thevoltage at the solenoid terminals, but its bri htness will indicatevisually whether the conductivity of the cell 16ha's been increased ordecreased. After the apparatus is once started it maintains a properlybalanced titration reaction without any attention, thus practicallyeliminating any labor cost and-yet insuring'exact- 1y regulated results.lVhile I have referred, for convenience, to a reaction between-sulfuric'acid and ammonia water, it will be understood that any suitablereagents, one of which supplies a gas to the reaction chambers, may besubstituted, as hereinabove explained.

Having thus described my invention, what I claim as new and. desire tosecureby Letters Patent-is: v

1. In the process of regulating a chemical reaction, one stage of whichcauses the presence at the reaction mixture of a gas that will induce acharacteristic conductivity in an electrolyte, the steps for findingwhether said stage has been reached, whichconsist in mixing saidelectrolyte with any gas from said reaction mixture and then -measuringthe conductivity of said electrolyte, said electrolyte being separatefrom the reaction ingredients.

. 2. In the process of regulating achemical reaction, one stage of whichcauses the presence at the'reaction mixture of-a 'gas that will induce acharacteristic conductivity in an aqueous electrolyte, the step ofdetecting the reaching of said stage by removing any gas from saidreaction mixture and mixing it with successive portions of saidelectrolyte and measuriilg the conductivities of said porstreams 0t-ions until said characteristic conductivity is found in one of them,said electrolyte being separate from said reaction ingredients.

3. In the process of regulating a chemical reaction in which thepresence of a gas at the reaction mixture indicatesan excess of one ofthe reagents, said gas having the property of inducing a characteristicconductivity in an aqueous electrotlyte, removing any gas progressivelyfrom said reaction mixture and mixing it with successive portions ofsaid electrolyte, measuring the conductivities of said portions, andwhen said characteristic. conductivity is found, adjusting the relativeproportions of the reagents to remove said excess, said electrolytebeing separate from the reaction ingredients.

4c. The rocess which comprises mixing t reagents to titrate them againsteach other, one of them supplying a gas at the reaction mixture when itis in excess,said gas having the vproperty of inducing a characteristicconductivity' in an aqueous electrolyte, removing any gas progressivelyfrom said reaction mixture and mixing it wlth a separate stream of saidelectrolyte, measuring the conducivity of said electrolyte at oneportion of its travel, and adjusting the rate.

of fiow of one of said streams of reagents relative to the other toremove said excess, whenever said characteristic conducitvity is foundin said electrolyte.

5. In apparatus for conducting chemical reactions, a fluid mixingchamber, means for feeding a stream of one reagent thereto, means forfeeding a stream of a second reagent thereto for titrating with saidfirst-named re-- agent, said second reagent supplying a gas increase anddecrease respectively of the conductivity of said stream of electrolyte.

c 7. In' automatic titrating apparatus, a chamber in which the reagentsare mixed, an electrolytic cell, means for renewing the electrolyte insaid cell, a suction device connected with'said cell and said chamberfor drawing gas evolved in said chamber into contact with theelectrolyte of said cell, a flow reguin said chamber when present inexcess, an

electrolytic cell containing an aqueous electrolyte, the conductivity ofwhich is changed by said gas, means for passing any of said gas fromsaid chamber into said electrolyte to cause changes in the conductivitythereof and means including electrical devices connected with said cellfor automatically regulating the rate of flow of one of said streamsrelative to the other in accordance with said changes in conductivity.6. In automatic titrating apparatus, a fluid mixing chamber, means forfeeding a stream of one reagent thereto, means for feeding a stream of asecond reagent thereto for titrating with said first-named reagent, saidsecond reagent, when in excess, supplying a gas in said chamber, anelectrolytic cell through which a stream of aqueous electrolyte passes,the conductivity of which is changed when any of said gas enters saidstream of electrolyte, means for passing any of said gas from saidchamber into said stream of electrolyte to, cause changes in theconductivity thereof and means for lessening the increasing the flow ofsaid second reagent relative to the flow of the first reagent inaccordance with the

